Please look at the Week 3 MHM pic. I think this is...

add molasses lower feeding a tiny bit before stirring it in

I think I’m agreeing with b4rns on this I think your light is too close and causing what is a mag deficiency. But adding more mag won’t help backing the light away reducing its intensity. This should allow the plant to keep up with your lights output. Best of luck moving forward

Ok if you mean the 3 leaves it's the strain, you know leaves that are new are lighter , I doubt very much it is lacking any nutrients , you need to test tun off , ph and EC

Your light is too close. Mag is the central molecule in the chlorophyll ion and is responsible for converting light into energy , it also gets used in the process. Before introducing Epsom salt you must be sure it certified for horticulture and pasteurized and sterilized. Adding more Mag won’t solve your problem as your plant is burning more Mag than she can absorb, back up your light further.

Take a picture under natural or white light, the purple light makes it really hard to actually tell anything about your plants. As for going overboard. Get an EC/TDS/PPM meter to check check the level of nutrient to use, specially if you plan to use epsom salts, that stuff is really strong and you most probably will burn your plant if you try to use it without a sure way to measure the strength of the solution